Recording Digital Output in Audition

Hey Guys and Gals,

I've been a Podcast for 2 1/2 years now. It's a pretty basic "two people talk" Pocast centered around landscape photography in German language.

So far I have used pretty basic methods of recording. 

I use an SM7 input via a Scarlett Solo and reroute the output that usual goes to the speaker into the second input of the Scarlett and record both of its inputs onto separate tracks.

It seems now that since I run a new machine this method leads to a lot of noise on the digital output (maybe the mainboard or the audiojack I don't know.

Either way, I remember recoding the audio straight in program by selecting the Digital Output as an Input for one of the tracks back in the day, as do many screencasting applications like OBS. Oddly enough I never was able to find out how to do this in Audition.  So I would be very thankful for some input on this issue. Thanks in advance.

/edit: Okay I found out how to use the "digital output" as an audio source for a track. However the issue now is that I can no longer select my Scarlet as a separate audio input for the first track. Is there any way to be able to use different audio sources for different tracks?